Short Range Forecast Discussion NWS Weather Prediction Center College Park MD 401 PM EDT Fri Jul 20 2018 Valid 00Z Sat Jul 21 2018 - 00Z Mon Jul 23 2018 ...A moderate risk of severe thunderstorms is in place across the Ohio and northwest Tennessee Valleys.... ...Heavy/excessive rain expected to impact the Ohio Valley and along the East Coast... ...Above normal temperatures to continue across the southern Plains along with the Pacific Northwest... A deep low pressure system is currently impacting the Upper Great Lakes region, with a strong cold front stretching southward through the Ohio and Middle Mississippi Valley, then eastward to the Central Plains. Copious amounts of moisture will pool along the front along with unstable air, generating strong thunderstorms with heavy rainfall through this region this afternoon and evening. The best convection is currently located across the Ohio Valley and portions of the Tennessee Valley. The Storm Prediction Center has outlined much of southern Indiana, central and western Kentucky, and Northwest Tennessee as being in a moderate risk for severe weather, while much of the rest of the region is in a slight or moderate risk. A slight risk of excessive rainfall is also in place across this region. The strong showers and thunderstorms are expected to continue throughout the evening and into the overnight. By Saturday, the system pushes eastward, and the cold front quickly dives southward. The Storm Prediction Center has outlined much of the southeast and eastern Tennessee Valley as having a slight risk of seeing severe storms through the day Saturday. Precipitation will also increase across the lower Great Lakes southward into Georgia and South Carolina, where the Weather Prediction Center has outlined a marginal risk for excessive rainfall. A developing low off the Carolina coast will slowly move northward along the Mid-Atlantic and into the Northeast through the weekend. Currently, heavy rainfall associated with this system is concentrated across the coastal portions of North and South Carolina where a slight risk of flash flooding will be a concern through tonight. As the low moves toward the New England coastline by late Saturday night/early Sunday morning, so too will the heavy rainfall and slight chance of excessive rain/flash flooding. Dangerous heat remains in place across much of the south-central and southwest United States and is expected to persist through the weekend. Excessive heat warnings and heat advisories are in place. High temperatures will reach well over the century mark across Texas and Oklahoma through this weekend. The Pacific Northwest will also continue to experience above normal temperatures--especially by the end of the weekend where temperatures could reach the mid to upper 90s. Elsewhere, monsoonal moisture will fire off thunderstorms across the Desert Southwest--where flash flooding could occur in favored terrain, desert regions, and urban corridors. A marginal risk of flash flooding is possible through Sunday. Wix Graphics available at www.wpc.ncep.noaa.gov/basicwx/basicwx_ndfd.php